I have a Yamaha 100hp 4 stroke. Its a great engine but this year I seem to have a strange new problem to solve. The fuel seems to be dropping out of the fuel line and requires pumping with the primer bulb for every single cold\first start of the day. Once started the boat seems perfectly ok to start throughout the day but if I come back the next day I have to reprime the bulb and find the fuel line appears to be totally empty. Anyone else had this issue ?

Nos - thanks, in that case I think I know exactly where this is. The gasket between the fuel sender unit and fuel tank has expanded and no longer makes a perfect
seal. I've ordered a new one already so hopefully that will be my problem solved.

I suspect it's not that gasket-unless Ribeye use some very unusual ( and extremely complex) tanks. It's more likely you just need to nip up or reseat a jubilee clip or change the primer bulb. It shouldn't be any drama to sort out.

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replace the primer bulb, this has a built in one way valve which often fails allowing fuel to siphon back to the tank. be careful as some bulbs need to 'hang' vertical for the valve to work properly. i had all this trouble a couple of years ago. i also fitted an electric pump which works on a push switch on the side of my console to prime the engine from the helm rather than wading round to the engine - this has proved to work very well.

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ok, heres an idea, if you have a clear inline filter you will notice that it never stays full, even if you try to fill it prior to connecting the fuel line to the engine. my guess is that the 'air gap' is actually vaporized fuel, and it is the expansion of that which causes the fuel to return to the tank.
i welcome other peoples ideas on this one!

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